Pneumatic tire / Sumitomo Rubber Industries, Ltd.

Title: Pneumatic tire.Abstract: [Solution] A tire 2 has a large number of dimples 62 on sidewalls 8 thereof. These dimples 62 are divided into dimples 62 of a first row I and dimples 62 of a second row II. The number of the dimples 62 per one row is 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 16, 18, 20, 24, 25, 30, 32, 36, 40, 48, 5060, 72, 75, 80, 90, 100, 120, 144, 150, 160, 180, 200, 225, 240, 300, 360, 375, 400, 450, 480, 500, 600, or 720. Preferably, the number of the dimples 62 of the second row II is equal to the number of the dimples 62 of the first row I.
[Object] To provide a pneumatic tire 2 for which processing of a mold is easy and which is excellent in durability. ...

TECHNICAL FIELD

BACKGROUND

In recent years, run flat tires including load support layers inside sidewalls have been developed and widespread. Highly hard crosslinked rubber is used for the support layers. Such run flat tires are called a side reinforcing type. In this type of a run flat tire, if the internal pressure is reduced due to puncture, a load is supported by the support layers. The support layers suppress flexure of the tire in a punctured state. Even if running is continued in the punctured state, the highly hard crosslinked rubber suppresses heat generation in the support layers. This run flat tire allows for running for some distance even in the punctured state. An automobile having such run flat tires mounted thereon need not be always equipped with a spare tire. The use of this run flat tire avoids change of a tire in an inconvenient place.

When running with the run flat tire in a punctured state is continued, deformation and restoration of the support layers are repeated. Due to the repetition, heat is generated in the support layers, and the temperature of the tire reaches a high temperature. The heat causes breakage of rubber components of the tire and separation among the rubber components of the tire. It is impossible to run with the tire in which the breakage and the separation have occurred. Run flat tires are desired which allow for running for a long period of time in a punctured state, in other words, run flat tires are desired which are less likely to cause breakage and separation due to heat.

WO2007/032405 discloses a run flat tire having a large number of fins on sidewalls thereof. The surface area of the tire having the fins is large. The large surface area promotes release of heat from the tire to the atmosphere. In the tire, the temperature is less likely to rise.

JP2009-298397 discloses a run flat tire having dimples on sidewalls thereof. The surface shape of each dimple is a circle. The surface area of each sidewall is large. In the tire, the dimples generate turbulent flow. The large surface area and the turbulent flow promote release of heat from each sidewall to the atmosphere. In the tire, the temperature is less likely to rise. The tire is excellent in durability during running in a punctured state.

JP2010-274886 discloses a run flat tire having dimples whose surface shapes are elongated circles. In the tire as well, release of heat from each sidewall to the atmosphere is promoted by the dimples. In the tire, the temperature is less likely to rise. The tire is excellent in durability during running in a punctured state.

SUMMARY

Elements such as fins, dimples, or the like are arranged along a circumferential direction at a predetermined pitch. Each element is formed by a mold.

The mold has elements each having a shape that is the inverted shape of the element of the tire. The elements of the mold are formed by machining.

In the machining, the pitch between the elements is generally controlled on the basis of a center angle (degree). When the center angle is an irrational number, control of the processing is difficult. When the center angle is an irrational number, the processing is advanced on the basis of a rational number close to the irrational number. An error gradually increases with the advance of the processing. Compensation for the error is made at any one of the elements. A program for controlling such processing is complicated.

An object of the present invention is to provide a pneumatic tire for which processing of a mold is easy and which is excellent in durability.

Preferably, the pitch between the elements is equal to or greater than 10 mm but equal to or less than 30 mm.

The tire may include a first row in which the large number of elements are aligned along the circumferential direction and a second row in which another large number of elements are aligned along the circumferential direction. Preferably, a number of the elements of the second row is the same as a number of the elements of the first row. Preferably, positions, in the circumferential direction, of the elements of the second row are displaced relative to positions, in the circumferential direction, of the elements of the first row. Preferably, the elements of the first row and the elements of the second row are alternately arranged.

Preferably, the tire includes:

a tread having an outer surface which forms a tread surface;

a pair of sidewalls extending from ends, respectively, of the tread substantially inward in the radial direction;

a pair of beads located substantially inward of the sidewalls, respectively, in the radial direction;

a carcass extending along the tread and the sidewalls and on and between the beads; and

a pair of load support layers located inward of the sidewalls, respectively, in the axial direction.

Advantageous Effects of the Invention

In the pneumatic tire according to the present invention, a large surface area of each side surface is achieved by the elements. The large surface area promotes release of heat from the tire to the atmosphere. The elements further generate turbulent flow around the tire. The turbulent flow promotes release of heat from the tire to the atmosphere. The tire is excellent in durability.

In the tire, a center angle between the elements arranged along the circumferential direction is a rational number, and thus processing of a mold therefor is easy.

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20140828|20140238571|pneumatic tire|[Solution] A tire 2 has a large number of dimples 62 on sidewalls 8 thereof. These dimples 62 are divided into dimples 62 of a first row I and dimples 62 of a second row II. The number of the dimples 62 per one row is 2, 3, 4, 5, |Sumitomo-Rubber-Industries-Ltd